Diffraction tomography – a 3D microscope

In the group “Nonlinear Photonics”, we investigate various aspects of the light-matter interaction in the field of optics with applications to such fields as biology, optical lattices, nonlinear materials, optical trapping or microscopy. Building customized imaging tools is very important since this way we obtain information about the crucial physical properties of the objects under investigation. In particular, non-absorbing objects that exhibit only a refractive index modulation are particularly challenging to image since they appear transparent under a regular bright field microscope. One of the solutions is to use the quantitative phase imaging (QPM) – a technique that visualize such weakly scattering samples but only in 2D. If the refractive index modulation is in all the 3D space, then one has to use a more advance technique - the optical diffraction tomography (ODT) microscope.

In analogy to the X-ray tomography (mostly known for medical applications) where the absorption coefficient of X-rays is mapped in 3D, the ODT allows for the quantitative, label free, three dimensional reconstruction of the refractive index changes. ODT is rapidly growing field that has already proved to be very successful in biology and medicine. The data collection procedure involves rotating the illumination source and collecting multiple hologram images. The procedure relays on the inversion algorithm that reconstructs the 3D distribution of the refractive index.

Master thesis

Diffraction tomography of refractive index changes: The aim of this project is to build the optical diffraction tomographic setup for the investigation of the refractive index changes at the micrometer range field of view. The work has a strong experimental component. In particular, such aspects as the assembly of various motorized stages, optical elements, optical beam alignment and the computer based data collection are crucial. The analytical part will involve the data processing, and algorithm development for the 3D tomographic reconstruction. The supervision will be provided by an experienced Postdoc.

This Master thesis is in accordance with the ongoing research of the group of Nonlinear Photonics. In our team, Master, PhD students and Postdocs discuss frequently about results, problems, scientific related articles and new ideas. We are looking for committed students who are interested in nonlinear photonics and want to work on current research.

Contact: If you are interested, please contact Dr. Ksawery Kalinowski, or Dr. Jörg Imbrock.